Electric step switch



Ncv. 3, 1942. A. J. M MA'STER ELECTRIC STEP SWITCH Filed Dec. 16, 1957 4Sheets-Sheet l fizz/612567":

' Jjyo aai'ez" A. J. MCMASTER 2,300,954 ELECTRIC ssrsr SWITCH 7 FiledDec. 16, 1937 4 Sheets-Sheet 2 Nov. 3, 1942.

W w Z wwwm il fi NOV. 3, 1942. McMAsTER' ELECTRIC STEP SWITCH Filed Dec.16, 1937 4 Sheets-Sheet 3 Nov. 3, 1942.

A. J. M MAsTER nmzcmzc STEP swmcn Filed Dec. 16, 1937 4 Sheets-Sheet 4Patented Nov. 3, 1942 ELECTRIC STEP SWITCH Archie J. McMaster, HighlandPark, Ill., assignor to G-M Laboratories,"lnc., Chicago, 111., acorporation of Illinois Application December 16, 1937, Serial No.180,058

Claims. (Cl. 172-126) The present invention relates generally to stepswitches operated by electric magnets, and relates more particularly toreciprocating magnetic motors adapted to operate such switches.

An indexing switch commonly includes a set of electric contactors whichare adapted to be stepped or indexed together from one'position to thenext through a series of positions. The contactors are adapted to engagea separate set of stationary contacts in each of their several indexedpositions and so can establish a different set of circuit connections ineach position. The contactors may be driven by a reciprocating magnetthrough a pawl, ratchet and detent mechanism. Such a switch indexes orsteps from position to position when its operating magnet isintermittently energized, and such a switch will self cycle or stepthrough a number of positions automatically if it is equipped withswitch contacts for controlling its own operating magnet.

Objects of the present invention include the provision of an improvedself cycling indexing switch, which is slow, deliberate and steady inaction, which is quiet in operation, which operates easily and gently soas to subject its working parts to a minimum of wear, tear and'operating strain, and which operates at an even and substantiallyconstant speed over a wide range of operating voltages applied to itsmagnet coil. These and other objects and advantages of my presentinvention will become apparent from the following description of aspecific embodiment of the invention. While this particular descriptionserves by way of example to illustrate the manner in which the inventionmay be used and practiced, the invention is not limited to theparticular details of construction of any embodiment or example. In thedrawmgs:

Figs. 1 and 2 are respectively a general elevation and a general planview of a self cycling indexing switch embodying my present invention,the operating parts thereof being illustrated in a rest position, orunoperated position, of the switch;

Fig. 3 is a partially broken away elevation of a view similar to Fig. 1but showing a different part of the mechanism. Specifically Fig. 3 in asection taken along the line 33 of Fig. 2;

Fig. 4 is a right end elevation, partly'in section, of the switch asseen in Figs. 1 and 3;

Fig. 5 is a partial right side elevation of Fig. 4, and therefore is apartial rear view of Figs. 1 and 3;

Figs. 6, 7 and 8 illustrate the mechanism shown in Fig. 1 in a series ofsuccessive operated positions; and

Figs. 9, 10 and 11 similarly illustrate the mechanism shown in Fig. 3 ina series of successive operated positions corresponding to the operatedpositions of Figs. 6, '7 and 8.

In Figs. 1 and 2 a stationary circular plate l2 of insulating materialcarries a series of concentric contact rings I4 and also a number ofindividual rivet-like contact buttons IE spaced uniformally on a seriesof concentric circles so as to lie also in radial rows. A rotatablecontact arm l8 of insulating material carries a series of fiveindividual contact assemblies 20 for engaging the individual contactrings l4, andcarries also a second group of five individual contactassemblies 22 for engaging the individual contact buttons l6.

The contactor assemblies 20 and 22 are of a construction shown andclaimed in my co-p'ending application Ser. No. 125,689 filed February15, 1937.

The contactor assemblies 20 and 22 ride over the left face of the disc22 as seen in Fig; 4', and electrical connections to the separate con-'tact rings l4 and contact buttons I6 are made by wires l5 and I! at theright side of the disc [2 as seen in Fig. 4. An aperture IS in the discI2 under the rings I4 permits the wires I 5 to be soldered directly tothe under surfaces of the rings l4 from the back face of the disc l2(the right surface as seen in Fig. 4). l

As may be seen in the partial sectional view of Fig. 4, the insulatingcontact disc I2 is bolted to a stud or shaft 24 which in turn is boltedto a formed sheet metal frame 26 so that the disc I2 is therebynon-rotatably secured to the frame 26. The contact arm I8, as is shownin Figv 2, is carried by a formed metal bracket 28. This bracket 28 anda peripherally notched disc 36, together with a reinforcing washer 32,are riveted to a bushing 34 which turns on the stud or shaft 24. Thebracket 28, and therefore the contact arm I8, is securely held innon-rotatable relation with the notched disc 30 by means of a blindrivet (not shown) partially punched in the bracket 28 and seated in aperforation (also not shown) in the disc 30. Also rotatably mounted onthe stud or shaft 24 is a bushing 36, shown best in Fig. 4, whichcarries a lever 38. The lever 38 is shown best in Fig. 3. It carries apawl 40 which is held resiliently in engagement with the peripheralnotches of the driving disc 3!! by a spring 42. A detent 44, smilar inconstruction to the pawl 48 is mounted on the frame 28 and is heldresiliently in engagement with the peripheral notches of the disc 38 bya spring 46. The lever 38 is adapted to be oscillated on the shaft 24 todrive the disc 39 and the contact arm l8 therewith in a directioncounterclockwise as viewed in Figs. 1 and 3. The lever 38 and pawl 4!!drive the disc 30 as the lever 38 swings towards the left as viewed inFigs. 1 and 3, and the detent 44 prevents retrograde motion of the disc30 while the lever 38 is returning towards the right. A driving spring48 is provided for moving the lever 38 in the direction which drives thedisc 30, and a magnet that is designated generally by the referencenumeral 50 serves to cook the spring.

An over-drive stop 52 serves to register disc 38 accurately and to stopit in the proper position. This stop is so placed that the driving pawl48 stops against it, and in so stopping becomes firm- 1y wedged inengagement with the peripheral notches of the disc 30. This arrangementpositively prevents forward motion of the disc 38 while the pawl 40 isresting against its overdrive stop 52. A lever stop 54 stops the lever38 itself and all of the moving parts directly connected thereto, suchas for example, the armature of the magnet 58. Both of the stops 52 and54 are adjustable, and the stop 52 should be so adjusted with respect tothe position of the stop 54 that the stop 54 takes the blow imparted bythe weight of the lever 38 and its directly connected parts, so that theoverdrive stop 52 stops only the pawl 40, the disc 30, and the lattersconnected contact arm l8. This adjustment is obtained by permitting aslight lost motion or back lash in the disc 30 when the lever 33 restsfirmly against stop 54.

The magnet 58 is shown in detail in Fig. 3. It includes a steel frameconsisting of a cylindrical shell 56 and two end plates 58, a magneticcore 60 and an energizing coil 82. The windings of the coil 62 areinsulated from the steel frame by layers of insulating material 64. Thecore 60 slides in a brass tube 66 which is closed with a plug 68 so thatthe core or plunger 88 is subjected to an air cushion dash-pot action orsnubbing action. A screw is adjustable to open and close an opening 12in the plug 68 to adjust the degree of air leakage which relieves orreduces the dash pot or cushioning action,

When either alternating or direct current is passed through the windingsof the coil 62 of the magnet 50, the magnet exerts a pull on its core 60to draw the core into the coil. This pull, of course, diminishes to zeroas the left end of the core 80 (as viewed in Fig. 3) comes into theposition in which it is flush with the outer surface of the left one ofthe two steel end plates 58. The link 14 connecting the core 50 with thelever 38 is of such length that the core 58 lies approximately in theposition of zero pull just described, when the pawl 4!] clicks over fromone notch of the disc 38 to the next as the lever 38 is cooked, that is,as the lever 38 is moved towards the left by the magnet 58 as viewed inFig. 3. No positive stop other than the magnet 58 itself is provided forlimiting the motion of the lever 38 towards the left. Accordinglysufficient space is left in the left end of the tube 85 to permit thecore 68 to move towards the left considerably beyond its position ofzero pull. It will move beyond that position only when carried there byits own momentum and the momentum of the lever 38 attached thereto.

As is best shown in Figs. 1, 2 and 4, a snap switch is provided forcontrolling the current sup plied to the coil of the solenoid magnet 58.This snap switch is adapted to be operated by the movement of the lever38 itself. The snap switch includes contacts I6 and a snap mechanism foroperating the contacts. That mechanism includes a snap follower 18 and aspring 80. The spring is stretched between the follower l8 and a bracket82 carried on the lever 38. This bracket 82 and the lever 38 serve asthe actuator member of the snap mechanism.

The snap follower 18 consists of a loop of wire, the specific shape ofwhich is best seen in Fig. 4. It is pivotally supported at an axis 84,by the plate or frame 26 and a bracket carried thereon. The loop 18rotates in this pivotal support between two adjustable eccentric stops,88 and 90.

In its normal position, shown in Fig. 1, the follower I5 is held againstthe stop 88 by the tension of the spring 88. As the lever 38 movestoward the left as viewed in Fig. l, the point of support of the spring83 on the bracket 82 also moves towards the left so that the line ofaction of the spring 88 is made to sweep through the axis 84 of thefollower 78. That is, the pull on the follower 18 is taken over the deadcenter position of the follower. As the line of action of the spring 80swings to the left of the axis 84, the direction in which the spring 88tends to rotate the follower 13 reverses so that the follower I8 isurged toward the left. Thereupon, the spring 80 rives the follower 18with a quick snap motion from its stop 98 its stop 88. As it comes intoposition against the stop 88, the snap follower 78 opens the contacts15, and then lying against the stop 88, the follower holds the contactsin their open position. When the lever 38 moves again towards the rightto its normal position against the stop 54, the spring 88 causes itsline of action 84 again to sweep across the axis 84 of the follower I8to snap the follower back into its normal position against the stop 98.When the follower I8 is in its normal position against the stop 90, thecontacts 16 close under the force of the inherent tension of thecantilever blades on which they are supported.

The contacts 16 are connected in series with the winding of the solenoidmagnet 50 as is shown in Fig. 1. A condenser 92 is connected across thecontacts 16 to reduce sparking at the contacts '16 when they are openedto interrupt the electric circuit. The use of the condenser in thismanner for spark suppression is well known in the art and forms no partof my present invention.

When completely assembled the mechanism is adjusted for proper operationas follows: Inasmuch as no adjustment is provided for the position ofthe detent 44, that detent determines the rest position or indexedposition of the notched disc 3|]. First the overdrive stop 52 isadjusted to stop the counterclockwise motion (as viewed in Fig. 3) ofthe notched disc 30 when that disc has rotated counterclockwise onlyslightly beyond the position in which it permits the detent 44 to snapinto a new notch. The overdrive stop 52 determines the limit of theforward or counterclockwise motion of the disc 38. Next the lever stop54 is adjusted to take the impact of the lever 38 so as to prevent themomentum of the lever 38 from driving against the overdrive stop 52.When the stop 54 is properly adjusted, the lever 38 may be held againstthe stop 54 and the notched disc 30 will exhibit a slight play about thepawl 48 in that it may oscillate slightly stopping against the pawl 48in both the forward and backward directions. The detent 44 should beheld away from the notched disc while the play at the pawl 40 is beingtested. This second adjustment may slightly shorten th stroke of thelever 38, and therefore th operation of the detent 44 must be checkedagain and if necessary the stops 52 and 54 should beslightly readjustedbefore further adjustments of the mechanism are made.

The radial rows of contacts l6 on th contact disc l2 are brought intoregister with the moving contacts 22 by rotating the contact disc I2 onthe stud 24. The disc I2 is clamped in position by a threaded nut and isheld against rotation by a lock washer interposed between the face ofthe disc I2 and the shoulder of the stud 24.

Next the eccentric stop 98 (Figs. 1 and 6) of the snap mechanism isadjusted. The armature 68 and lever 38 are moved by hand towards theleft into the position in which they are shown in Fig. 9. In thisposition the lever 38 has moved somewhat beyond the point at which thepawl 48 snaps into a new notch. While the lever 38 is held in thisposition the eccentric stop 90 (see Figs. 1 and 6) is rotated so as tomove the snap follower 18 towards the left into the position in which itis shown in full lines in Fig. 6. In this position of the apparatus, theline of action of the spring 88 passes through the pivotal axis 84 ofthe snap follower 18 so that the follower 18 is on the verge of snappingto the left into the position 18a as shown in dotted lines in Fig. 6.Next the lever 38 is returned towards the right into the position shownin Fig. 11. In this position the lever 38 is still somewhat removed fromits stop 54 and the detent 44 has ridden up onto thetip of a tooth ofthe notched wheel 38. With the lever 38 in this position, the eccentricstop 88 (Fig. 8) is adjusted to move the snap follower 18 towards thleft until it is in the position shown in full lines in Fig. 8. In thisposition of the apparatus, the snap follower 18 is on the verge ofsnapping to the right into the position 18b shown in dotted lines inFig. 8.

Next the mounting position of the contact assembly is adjusted bysliding the bracket 11 under the heads of its mounting screws (see Figs.1 and 7) until thecontact assembly is in such position that the snapfollower 18, when it lies against the eccentric stop 88 (Fig. '7)engages the vertex of the angular bend at the right hand end of theblade 19. With the blade 19 so adjusted the spring tension of thecontact blades can exert little or no force, other than friction, whichwill either retard or aid the motion of the snap follower 18 away fromits stop 88. Next the two upper blades which support the contact buttons18 are bent into such an adjustment that they engage each other firmlywhen the snap follower l8 lies against the stop 98 (normal position)leaving the blade 19 free, and such that the contacts 18 separate aconsiderable distance when the snap follower 18 moves into positionagainst the stop 88 to lift the tension spring I9.

Finally the air leak screw 18 (See Fig. 3) is adjusted to provide thebest value of air leakage from the dash pot. It will be apparent thatsome leakage can occur around the core 60 itself by the passage of airthrough the clearance space between th solenoid core 60 and the brasstube 86 in which it slides. During the adjustment of the screw 18 theswitch is operated from a power supply of the maximum voltage on whichthe switch is intended to operate. When the power is applied to the twoconnecting wires 9| and 93, the switch will operate automatically andcontinuously, indexing its moving contacts 22 from on radial row ofcontacts l8 to th next each time that the armature and lever 38reciprocate. Inasmuch as the lever has no stop to limit its motiontowards the left, if the air leakage from the dash pot space is toogreat, the armature 68 will drive against the plug 68 (Fig. 3). Theforce of the armature 68 repeatedly striking against th plug 68 createsconsiderable noise and also imposes severe operating strains upon themechanism. Whil the apparatus is operating on the highest voltage forwhich it is intended, the screw 10 is turned in to partially cover theopening 12, until the switch quiets down. The quieting will indicatethat the solenoid'armature or plunger 60 has ceased to strike againstthe plug 88.

When so adjusted the switch will operate quietly and reliably at anyvoltage between the maximum voltag forwhich it is adjusted and theminimum voltage which will supply sufficient current to the winding ofthe magnet 58 to cook the driving spring 48. Furthermore the speed ofoperation will change very little with the voltage applied to the coil.

Both the dash pot restraint imposed upon the operation of the solenoidarmature, and the snap acting control switch'which includes the snapfollower 18, help to provide the constant speed of operation of thisswitch. An appreciable share of the total time consumed by a cycle ofoperation or oscillation of the lever 38 consists in the time requiredfor the operation of the snap follower 18. This time is practicallyindependent of the voltage which may be applied to the winding of thesolenoid coil. The lever 38 undoubtedly moves somewhat faster when ahigh voltage is applied to the solenoil coil, but under such conditions,the lever 38 moves a greater distance towards the left and thereforewhile it moves faster it must move through a greater distance. Thiscircumstance aids in keeping the total time for each oscillationsubstantially constant over wide ranges of voltage.

The snap switch by itself improves the reliability of operation andmakes certain that each stroke of the solenoid will be a full stroke.The dash pot provides a cushion stop for the plunger, reduces noise andeases operating strains. The two together cooperate to drive theindexing switch quietly, reliably and at a substantially constant speedover a wide range of operating voltages.

It will be apparent that the present invention is not limited to thespecific form or construction herein shown and described but that it iscapable of various modifications. Accordingly the invention is to belimited only within the scope of the appended claims.

I claim:

1. In an indexing mechanism, a member to be indexed repeatedly in onedirection, ratchet teeth on said member spaced in accordance with theindexing steps to be made by said member, a pawl for engaging said teethto drive said member, a spring for driving said pawl in one direction todrive said member, means for limiting the driven motion of said pawl,said means including a stop for simultaneously stopping thespring-driven motions of said pawl and said member, an electromagnet fordriving said pawl in the other direction to cook said spring, contactsoperated by said magnet for controlling the energizing of the magnet todeenergize the magnet when the spring is cocked, said pawl being free tomove in said other direction beyond its cocked position, a stop forpreventing said pawl from moving far enough beyond said cocked positionin said other direction to pick up an extra ratchet tooth on saidmember, and a dash pot for retarding th spring cocking motion of saidpawl and for stopping it after said magnet is deenergized but beforesaid pawl encounters a positive stop in said other direction.

2. The combination of claim 1 wherein there is included a spring snapmechanism operated by said magnet for operating said contacts, said snapmechanism including a snap follower and an actuator therefor such thatsaid actuator moves to bias the snap follower and said snap followerresponds by executing a sudden snap motion after the actuator reaches acertain position, said snap follower snapping between two extremepositions and lying normally in one of said extreme positions, said snapmechanism and said contacts thereof being so constructed and arrangedthat they operate to deenergize said magnet only when said snap followerlies substantially in its other extreme position.

3. In combination in a reciprocating electric magnetic motor, areciprocable driven member biased to a normal position, an electromagnetfor driving said driven member out of its normal position, a snap switchoperated by said driven member, said snap switch including a springdriven snap follower and a link connecting said follower to said drivenmember to be actuated thereby, said follower and link including a springfor driving said follower, said snap follower having a normal extremeposition and another extreme position, said switch including contactsoperated by said follower for controlling the energizing of said magnetand so constructed and arranged that they deenergize said magnet onlywhen said snap follower lies substantially in said other extremeposition, said device being so constructed and arranged that said drivenmember is free to move in its magnet driven direction beyond itsposition at which said snap switch first tends to operate.

4. In combination in a reciprocating electromagnetic motor, areciprocable driven member biased to a normal extreme position thereof,stops for defining said normal extreme position and also an oppositeextreme position for said driven member, an electromagnet for drivingsaid member out of said normal position towards said opposite position,and control means for said electromagnet operated by said driven memberfor controlling the energization of said magnet, said control meanscomprising a spring snap mechanism including a snap follower actuated bysaid driven member and adjusted to snap from a first to a second extremesnap position when said driven member is in substantially said normalposition, and from said second to said first snap position when saiddriven member is intermediate its two extreme positions andsubstantially out of its said opposite extreme position, and comprisingalso spring closed electric contacts at said first snap positionactuated to open position by said snap follower but only when said snapfollower is substantially in said first extreme snap position, andcircuit connections connecting said contacts in series with said magnetfor controlling the electric energizing circuit thereof.

5. The combination of claim 4, wherein there is included a dash pot foropposing the magnet driven motion of said driven member.

ARCHIE J. MCMASTER.

